The present invention relates to a dental implant, and more particularly relates to an implant suitable for repairing lost canine teeth.
It is known that lost teeth can be repaired with artificial teeth which are mounted on artificial tooth roots, i.e. dental implants implanted in an alveolar bone.
Varieties of dental implants are proposed, and the present inventor has also proposed a very efficient blade-type implant, which has matured to U.S. Pat. No. 5,302,128.
The blade-type implant requires a long and narrow groove to be implanted in an alveolar bone, and is useful for repairing lost molar teeth, however, it is not suitable for repairing lost canines, because canines are located at the edge portion of the alveolar bone, and accordingly, the narrow and long groove which is capable of strongly supporting the implant cannot be dug.
A prior art implant suitable for repairing a lost canine has a structure provided with a rod-form body which should be implanted in an alveolar bone, and a pillar-form head which is mounted on the upper edge of the body and supports an artificial tooth.
In order to anchor the prior art implant, a hole which is adapted to receive the body is dug in the alveolar bone, an implant is inserted into the hole for an initial securing by a frictional connection, and after a certain period of time, the implant can be firmly secured with newly grown bone tissues of the alveolar bone.
The above known implant has the following disadvantages:
It is very difficult to form a hole in an alveolar bone, which should be completely fit to an implant to be embedded, because the practice is performed in the patient's mouth. When the size of the hole is too large for an implant, the embedded implant will wobble, and when the hole is too small, the implant cannot be inserted into the hole smoothly.
In the former case, the patient has to wait for a certain time period until the embedded implant is firmly secured by newly grown bone tissue, and in the latter case, the patient has to have repeated surgery until the hole becomes large enough to be adapted to receive an implant.
It is technically impossible to have a perfect phase contact between the outer peripheral of the rod form body and the inner peripheral of the hole, non-uniformity of the phase cannot be avoided, and cracks of the alveolar bone in the width direction have often been experienced, when the body is hammered to embed in the hole with a mallet.
Even when the implant adapts readily to the hole, the embedded implant is apt to move due to supersonic vibrations of the turbine for the dentist, and accordingly, dentists must avoid use of the turbine for treatment of teeth in the neighborhood of the implant.
In order to obtain stronger friction connection of the contact phase, the size of the hole is usually made as narrow as possible, and risks of cracks of the alveolar bone increase at the time of the insertion of the implant.
It is true that the contact phase between the implant and the hole is made larger, the friction connection force becomes stronger, however, an enlargement of the contact phase of the hole toward the periphery should be restricted by the next teeth, and its solution is directed to an enlargement of length to as deep as possible. Dentists have tried to make holes as deep as possible up to the neighborhood of mental foramen or lower alveolar vessel, and this surgery includes high risks.
Legs of the lower portion of the implant usually reach inside of soft sponge bone of the alveolar bone, the implant sinks unnecessarily deep if it is tapped into the hole with a mallet, and it also gradually sinks too much due to daily bites after the completion of surgery.
Furthermore, holes for inflow of blood into bone tissues which contact the implant body are provided with the body of the implant. However, the number of holes is limited to as few as possible in order to increase the contact phase between the outer periphery of the body and the inner periphery of the holes for the implant as large as possible. Accordingly, effective contact of bone with the body cannot be obtained in the event that growth of new bone tissue is insufficient for lack of necessary blood supply, or bone tissues are completely destroyed (necrosis) in the event that blood supply is not totally available.
As is explained above, dental implants include many clinical problems hard to solve and accordingly, have not been very popular yet.
In spite of the above disadvantages, the dental implant is fully acknowledged as useful, e.g., for supplemental support of long span bridges, and technological improvement has strongly been demanded in this field, especially from patients who have psychological aversions to artificial teeth.